New fuel cell material can run efficiently in reverse, storing energy

Lithium batteries can readily smooth out short-term hiccups in
the supply of intermittent renewable energy. But they’re not ideal
for long-term storage, since they’ll slowly discharge. They also
aren’t great for large quantities of energy—to store more, you
keep having to buy more battery. Because of these issues, there has
been research into a number of technologies that scale better, like
flow batteries and
renewable fuel production. But these pose their own challenges,
both chemical and economic.

But researchers are now reporting a possible solution to some of
these problems: a fuel cell that can be run efficiently in both
directions, either using hydrogen or methane to produce electricity
or using electricity to produce these fuels. Their measurements
suggest that, after doing a complete cycle, they get out 75 percent
of the electricity they put in to start with.

Limitations abound

Batteries, as we mentioned above, don’t work for longer-term
storage, as they will typically lose charge slowly. They’re also
expensive, as adding capacity means adding more batteries. Flow
batteries solve some of these problems by storing the charged and
discharged forms of a chemical in different tanks; larger or
additional tanks are cheap, making expanded capacity relatively
simple and inexpensive. But flow batteries aren’t as efficient as
traditional batteries, and the chemicals they use can be toxic or
corrosive.